A number of liquid chromatography systems utilize a variety of configurations specifically tailored to particular chromatographic applications. In many liquid chromatographic systems, elevated temperatures are helpful for the analysis and resolution of liquid samples, or dissolved solutes, in mobile phases. Generally, increased liquid mobile phase temperature reduces mobile phase viscosity resulting in increased mobile phase flow rates through the stationary phase. Elevated temperature can also maintain or improve the resolution and elution profiles of chromatographic separations and assays. As a result, a number of liquid chromatography systems in use today utilize heating means for elevating the assay temperature, including mobile phase temperature, as the mobile phase is directed through the chromatography system.
Chromatographic heating systems in use today are generally operated around 80° C. or below, and have several characteristics which compromise the overall efficacy of elevated temperature liquid chromatography. Some existing systems utilize conductive or convective heating means directed to the chromatographic column to impart heat energy to the mobile phase for elevated temperature analysis of dissolved samples/analytes. Such techniques fail to properly “pre-heat” the mobile phase prior to application onto, or injection into, the chromatographic column, which generates mobile phase temperature profile gradients radially and axially within the chromatographic column. Mobile phase temperature gradients are, in general, undesired in liquid chromatography applications because it can result in loss of resolution and peak broadening. This problem has been addressed by a number of methods, most notably mobile phase pre-heaters that are designed to heat mobile phase to a desired temperature prior to application onto the chromatographic column. These systems are largely inefficient because the temperature of the pre-heated mobile phase is typically measurably different than the temperature of the chromatography system, which can create undesirable temperature gradients within the column.
Some chromatographic heating systems utilize a radiant or convective oven, which can house one or more of the chromatographic system components in order to elevate the temperature of the mobile phase being transported to the column, as well as the column itself. Such ovens are typically large in size and have minimal success in elevating temperatures uniformly. For example, the desired set temperature may not be reached in all locations within the oven, which creates temperature gradients within regions of multi-component chromatographic systems depending upon the position of each component within the oven. This can result in large temperature differences between the set point and even the external temperature of the chromatographic column of over 20° C. (±2° C.). Further, the temperature within the chromatographic column can vary both radially and axially, due to differences in temperature of the incoming mobile phase, as compared to that of the oven and/or the column separation media (stationary phase). Thus, a common problem experienced with oven heating systems is that the column temperature varies from the desired temperature set point, due either to temperature gradients within the oven, ineffective thermal transfer, and/or slow thermal equilibration of the column under actual operating conditions.
Thus, there remains a need in the art for an insulator that maintains consistent heat over the entirety of the chromatographic column, so as to minimize temperature gradients between pre-heated mobile phase and the column media, as well as axial and radial temperature gradients within the column itself. Such insulators can also maintain a desired column set point temperature during a chromatographic experiment throughout the chromatographic column. The present invention provides an economical thermally insulated apparatus for efficiently and effectively insulating a chromatographic column for assays and separations performed at elevated temperatures.